Capital cost retrofit

Yoon, H., Theodare, F., Burke, F., Koch, B.J. and Corder, W.C. (1986) "Low capital cost retrofit SOj control technologies for high sulfur coal applications", Proc. 79 th Annual Meeting of Air Poll. Cont. Assoc. Minneapolis, MN. 

Particle Segregation Mechanisms. Segregation is the process by which an assembly of soHd particles separates as it is being handled. This often results in cosdy quaUty control problems due to the waste of raw or finished materials, lost production, increased maintenance, and capital costs required to retrofit existing faciUties. 

Various criteria were proposed for the optimal selection of the equipment configuration and the number and sizes of units. In grass-root design, the capital cost of equipment is mostly used as the optimization criterion. In retrofit design a more appropriate objective function seems to be the net profit, which has to be maximized. Papageorgaki and Reklaitis (1993) formulated the criterion as follows ... 

If the capital cost of new heat transfer area is expressed in the form of Equation 18.6, then this will lead to poor retrofit projects. The problem with Equation 18.6 is that the optimization is likely to spread the new heat transfer area in the network in many locations, without incurring a cost penalty associated with the many modifications that would result. To ensure that new heat transfer area is not spread around throughout the existing heat exchanger network, a capital cost correlation should be used that is of the form ... 

It should be noted that a resequence or repipe does not involve zero capital cost, even though no new heat exchanger equipment might be purchased. The pipework modifications for a resequence or repipe might be very expensive. Also, equipment might need to be relocated. Methods for capital cost estimation for retrofit were discussed in Chapter 2. 

The vendor supplied an unspecified case study that compared the costs of an existing pump-and-treat system with a pump-and-treat system that had been retrofitted to accommodate an FE ACTIVE. The projected life-cycle cost (adjusted for an inflation rate of 4% and a rate of interest of 5%) of the existing pump-and-treat system was calculated to be 3,930,000 (1996 dollars). The life-cycle cost (adjusted for a 4% inflation rate and a 5% interest rate) of the FE ACTIVE retrofit system was calculated at 945,000 (1996 dollars). Both estimates included capital costs, operation and maintenance expenses, and the cost of groundwater monitoring. Similarly, had the FE ACTIVE system been installed initially, its life-cycle cost would be 1,630,000 (1996 doUars). 

Usually the ammonia concentration of the recycle is 3% to 4%, but reducing this amount to 1.5% can increase plant capacity by about 2.5%. However, the additional separation can often represent a significant addition to the capital cost of the plant and may not be economical for a retrofit (depending on operating pressure). However lower ammonia concentration in the recycle can be reviewed for a grass root project where capacity gains can be realized with an additional investment212. 

Table 5.6 Approximate fixed capital cost calculations for the retrofits...

One of the interesting features of the two-phase digestion process is that it can be retrofitted to an existing anaerobic digestion plant to effectively double its treatment capacity at a considerably reduced capital cost compared to the cost of a grassroots plant of the same additional incremental capacity. The U.S. Environmental Protection Agency s projection of new anaerobic digestion capacity needed in the United States for municipal wastewater treatment in... 

Spray-dryers are simpler and more compact than conventional wet scrubbers and have a lower capital and operating cost. Also, they do not produce large quantities of wastewater, and the spent absorbent is dry, thereby eliminating the need for thickening and filtration of the sludge. However, if the same dust precipitator is used for both the fly-ash and fhe spray-dryer product, the mixture of fly-ash and spent absorbent that they produce is unmarketable, and must be disposed of. Also, they require more expensive absorbents than conventional wet scrubbers. They are most suitable for retrofitting small plants that burn medium-sulfur coals, where capital costs and space restrictions are more of a consideration. ... 

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